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Zai is probably the most renowned technology which has been developed based on indigenous knowledge (Sewadogo 2011) and traditionally used to improve poor and bare soils.
After digging the Zaipits, they are filled with organic materials such as manure, compost or dry biomass. This leads to increased microbial activities which in return increases the rate of water infiltration during the rainy season. This creates a micro-environment that increases drought resistance and improves crop yields. Zai pits are most suited for ASAL areas where infertile, encrusted soils receive low and often highly unreliable rainfall causing the small-scale farmers face constant challenge to produce enough food to feed their families and generate much needed incomes. Consequently, Zai pits as an innovation addresses issues of land degradation, soil infertility and moisture retention.
Through digging of zai pits; degraded hand-pan soils that is impossible to plough can be made productive rather than being abandoned. Zai pits play a very important role in controlling run off since the rain water is tapped in them, conveniently close to the crop roots thus playing a major role in water harvesting.
Harvest rain water: The small pits acts as micro catchments that collect water and sediment, the soil placed downhill from each pit enhances their water harvesting function. The added organic material improves the infiltration and retention of water in the soil. The micro catchments help to mitigate against periods of drought that occurs frequently in ASAL regions (Zougmore et al 2004)
Concentrate fertility: Zai pits concentrate fertility near the crop root zone, wind or runoff driven debris, including leaf litter from nearby vegetation is caught in the holes. Fertility gained from these sediments is mixed with organic or mineral fertilizer making them highly fertile. According to Sewadogo (2008) this also increases carbon, nitrogen, phosphorus and soil pH.
Accelerated decomposition: In the semi arid tropics, termites are abundant, their activities contribute significantly to decomposition of organic matter and nutrient cycling in the soil (Mando and Brussaard 1999). In the process of decomposition added to the favourable zai pits environment that accelerates the decomposition making the zai pits to remain productive for longer period compared to areas without zai pits.
Reduced competition: zai pits ensures that competition for moisture, manure and pesticides by weeds are highly reduced. This is because the crop is developed on “artificial environment” which is controlled and thus weeds and pesticides are disadvantaged. However, in case of growth of weeds, weeding should be done paying attention to the downhill side of each pit not to destroy the mounds of soil and reduce their water catchment function.